Se Han Kwon

Growth of CuInSe2 thin films by high vapour Se treatment of co-sputtered Cu-In alloy in a graphite container

Abstract The crystallization of CuInSe 2 thin films by high Se vapour selenization of co-sputtered Cu-In alloy precursor within a partially closed graphite container is reported. X-ray diffusion (XRD) analysis of the Cu-In alloy films displayed mainly the CuIn 2 and Cu 11 In 9 phases. A three-fold volume expansion was recorded in all the selenized CuInSe 2 films at 500–550°C. Large and densely packed crystals with sizes of about 5 μm were exhibited by the films irrespective of whether they were Cu-rich or In-rich. Single phase chalcopyrite CuInSe 2 structure with preferential orientation in the (112) direction were obtained. Films with a wide range of compositions (Cu/In of 0.43–1.2 and Se/(Cu+In) of 0.92–1.47) were fabricated. All the films where Se rich, with the exception of samples with very high Cu content. The measured film resistivities varied from 10 −1 to 10 5 Ω-cm in consistence with the increasing Cu content of the alloy precursor during deposition. The alloy films with very high In content yielded the CuIn 2 Se 3.5 or CuIn 3 Se 5 compound as determined from XRD and EDX analyses. A study of the reaction mechanism performed between 250 and 550°C indicated that the crystal growth was assisted by the formation of the CuSe flux agent. The development of a suitable window layer to test the photovoltaic properties of these films is currently in progress.

Growth of CuIn3Se5 layer on CuInSe2 films and its effect on the photovoltaic properties of In2Se3/CuInSe2 solar cells

Abstract The growth of CuIn3Se5 layer on bulk CuInSe2 films has been studied for the fabrication of CuInSe2 solar cells, using the three-stage process which involved the sequential evaporation of In–Se, Cu–Se, and In–Se elemental sources. After growing CuInSe2 films, the film surface was converted to a defect chalcopyrite (CuIn3Se5) compound. The X-ray diffraction and AES depth analysis indicated the formation of the CuIn3Se5 phase on the CuInSe2 surface. By the formation of the CuIn3Se5 phase, the absorption edge was shifted from 1200 to 1000 nm wavelength and the binding energies of Cu, In, and Se were shifted to higher energies. The current–voltage curves of In2Se3/CuInSe2 cells fabricated with a thick CuIn3Se5 layer on a CuInSe2 film displayed a kink effect which was possibly caused by the increase of series resistance and light absorption in the CuIn3Se5 layer instead of the junction region. The cells with a thin CuIn3Se5 layer at the In2Se3/CuInSe2 interface yielded solar efficiency of 8.46% with an active area of 0.2 cm2.

Effect of CuIn3Se5 layer thickness on CuInSe2 thin films and devices

CuInSe 2 thin films were prepared by a three-stage sequential co-evaporation of In-Se, Cu-Se, and In-Se elements for photovoltaic application. After growing CuInSe 2 films, the film surface was converted to an ordered vacancy compound (CuIn 3 Se 3 ). The presence of a CuIn 3 Se 5 layer on the CuInSe 2 surface was confirmed by XRD and AES. By the formation of the CuIn 3 Se 5 phase on the CuInSe 2 surface, the absorption edge was shifted from 1200 A to a shorter wavelength. On the CIS films, an In 2 Se 3 buffer layer instead of the commonly known CdS layer was employed and deposited in the same evaporator without breaking the vacuum system. The ITO/ZnO/In 2 Se 3 /CuInSe 2 cells with a thin CuIn 3 Se 5 layer at the In 2 Se 3 /CuInSe 2 interface yielded a solar efficiency of 8.46% with an active area of 0.2 cm 2 which is considered high efficiency regarding no Ga in the CIS absorber layer.

Electrical properties of CuInSe2 films prepared by evaporation of Cu2Se and In2Se3 compounds

Abstract We prepared CuInSe2 films by evaporating In2Se3 and Cu2Se compounds instead of elemental sources. The resulting CuInSe2 film grown at 680°C had a smooth and dense microstructure with the grain size of 2 ∼ 3 μm. But the CuInSe2 films were Cu-rich, with a low resistivity of about 0.1 Ω cm. So we conducted H2 post annealing to control the electrical resistivity and composition of CuInSe2 films. In a H2 atmosphere, the resistivity increased to about 100 Ω cm by annealing at 350°C for 1 h. The resistivity decreased again when the annealing temperature was above 350°C. This resistivity change might be related to the contents of Cu, In, Se atoms and the valency states of Cu and In ions in the films. We discussed the reason of resistivity change caused by H2 post annealing in this paper.

Preparation of CuInSe2 thin films by selenization of co-sputtered Cu–In precursors

CuInSe2 thin films have been prepared by high Se vapor selenization of co-sputtered Cu–In alloy precursors within a partially closed graphite container. Cu–In alloys with different compositions were investigated. X-ray diffraction (XRD) analysis of the films showed mainly CuIn2 and Cu11In9 phases and the Cu11In9 peak intensity was found to increase as the alloy composition tended towards Cu-rich. A linear dependence of the alloy composition on the Cu/In deposition power was observed from energy dispersive analysis by X-rays (EDX). A three-fold volume expansion was exhibited by all the CuInSe2 films after selenization at 500–550 °C. Scanning electron microscopy (SEM) analysis of the films showed large and densely packed crystal structures with sizes above 5 μm. The CuInSe2 films exhibited single phase chalcopyrite structure with preferential orientation in the (1 1 2) direction. The EDX composition analyses of the films showed Cu/In ratio ranging from 0.43 to 1.2, and Se/(Cu+In) ratios from 0.92 to 1.47. The measured film resistivities varied from 10-1 to 105 Ωcm. The Cu–In alloy precursors with Cu/In ratio less than 0.70 were found to form CuIn3Se5 a defect chalcopyrite compound. All films were Se rich, with the exception of samples with very high Cu content.© 1998 Kluwer Academic Publishers

Characterization of Cu(In,Ga)3Se5 thin film for top cell in CIGS tandem solar cells

Cu(In,Ga)3Se5 films were deposited on soda-lime glass substrate by three-stage co-evaporation process. In the film, the band gap increased as the Cu content decreased and also as the Ga content increased. The grain size became smaller as the Ga content increased. In the Cu1.29(In1-xGax)3Se5 system, the maximum hole concentration was 1x1015 /cm3 when the Ga content was 0.5 and its band gap was 1.45 eV. Comparing the conventional CIGS solar cell with Cu0.8(In0.7Ga0.3)Se2 film, the series resistance is too large, indicating that further p-type doping in the Cu(In,Ga)3Se5 film is necessary to improve cell efficiency for the top cell application in CIGS tandem solar cells.

Growth of CuIn/sub 3/Se/sub 5/ layer on the CuInSe/sub 2/ film and its effect on the photovoltaic properties of In/sub 2/Se/sub 3//CuInSe/sub 2/ solar cells

The growth of CuIn/sub 3/Se/sub 5/ layer on CuInSe/sub 2/ films has been studied for the fabrication of CuInSe/sub 2/ solar cell, using the three-stage process. After growing the CuInSe/sub 2/ film, the film surface was quickly converted to a possible ordered vacancy compound (CuIn/sub 3/Se/sub 5/). AES depth analysis indicated the presence of a CuIn/sub 3/Se/sub 5/ layer on the CuInSe/sub 2/ surface. The energy bandgap shifted from 1.04 to 1.24 eV by the formation of CuIn/sub 3/Se/sub 5/ phase on CuInSe/sub 2/ surface. Because the lattice parameters of CuIn/sub 3/Se/sub 5/ are smaller, the XRD peaks were shifted to higher 2/spl theta/ values. In/sub 2/Se/sub 3//CuInSe/sub 2/ cells with a thin CuIn/sub 3/Se/sub 5/ layer at the interface yielded solar efficiency of 8.46% with an active area of 0.2 cm/sup 2/. The device fabricated from the films with a thick CuIn/sub 3/Se/sub 5/ layer on CuInSe/sub 2/ film displayed a double diode effect which was possibly caused the increase of junction interface.

MAGNETIC AND RECORDING PROPERTIES OF SPUTTERED COCRTA/CR THIN-FILM MEDIA

The magnetic and recording properties of CoCrTa/Cr, longitudinal, magnetic, recording media, with various Cr contents, were investigated by changing the deposition temperature, the Cr thickness and the CoCrTa thickness. The Cr content of the CoCrTa magnetic layer was varied from 10 to 14 at % Cr and the films were deposited on textured NiP/AIMg substrates by direct-current (d.c.) magnetron sputtering. Both the circumferential magnetic coercivity (Hc) and the coercivity orientation ratio (Or) of the media increased as the deposition temperature increased. The optimum Cr thickness was 50 ∼ 70 nm; below this optimum value both Hc and the Or were small, and above this value the Or decreased. As the CoCrTa thickness increased, the Or continuously decreased, while Hc had a maximum of about 1600 Oe near the 40 nm thickness. The signal-to-noise ratio of the CoCrTa/Cr films increased as the deposition temperature, the Cr thickness and the CoCrTa thickness increased. However, the bit shift was lowest when the thicknesses of the CoCrTa and Cr layers were 50 ∼ 60 nm and 50 ∼ 70 nm, respectively. The CoCrTa magnetic films with 10 at % Cr had the highest signal to noise ratio of 33 dB and the lowest bit shift of 9 ns. Our results showed that the Or factor is an important parameter for high-performance recording characteristics as is a high Hc.